1. Field of the Invention
The present invention relates in general to a laptop computer and associated docking station, and more particularly to a method of hot docking and undocking without the need to place the computer system in a standby or suspended mode.
2. Description of the Related Art
Performance improvements in microprocessor and memory systems have resulted in computers so powerful that they are now capable of performing tasks that before could only be performed by large mainframe computers. Technological change has been especially swift in the area of portable computers, where power consumption efficiency is balanced against features, cost, size, weight and performance. Design choices are particularly challenging since many computer users desire the portable computer to provide functionality similar to that of a desktop unit. The term "portable computers" is used broadly to denote the class of computers powered by battery or solar power. Those familiar with portable computers will recognize other labels such as: luggable, laptop, notebook and hand-held. These categorizations are used to designate certain marketing segments of the larger portable computer market.
Many options are available to the computer system designer. While simply designing around the highest performance processor available goes a long way towards providing a high performance product, it is not enough in today's market. The processor must be supported by high performance components and a high performance I/O (input/output) bus. Several standardized I/O buses are available to the system designer including: ISA (Industry Standard Architecture); EISA (Extended Industry Standard Architecture); and PCI (Peripheral Component Interface). Today's computers are typically designed with some combination of the three to provide the user with the performance of PCI and backward compatibility to ISA or EISA. These three buses are familiar to those skilled in the art.
Certain performance criteria also involve special features of the computer that distinguish one manufacturer's computer from a competitor's. These added features can result in increased size and weight. For example, software and multimedia documents can require large amounts of storage, and a very high capacity hard disk drive is often necessary. High capacity disk drives, however, are usually larger and heavier than is desirable for a portable computer. It is also desirable to have the ability to add functionality to the portable computer. Typical expansion bays, however, can also compromise a portable system's size advantages.
One known method of providing extra features without negatively impacting size and weight is through the use of an expansion base unit (also referred to as a docking station). An expansion unit is a non-portable unit that typically operates from AC power and resides on the user's desktop. When the user is working at the desk, the portable computer plugs into the expansion unit to provide added functionality. For example, the expansion unit may have a network interface unit for connecting to a local area network, a high capacity disk drive, a CRT, a full-size keyboard, a floppy or CD-ROM drive and other peripherals.
The connection between the portable computer and the expansion base unit is typically proprietary since no standard has yet evolved. One known way to couple the portable computer to the expansion base unit is through the existing I/O bus. In a portable computer having a PCI bus and an ISA bus, either bus might be used to connect to the expansion base unit. For highest performance, the PCI bus is preferable.
Current methods of connecting portable computers to docking stations are less than ideal. Using what is known as "cold docking," the user must close all applications and turn off power to the system prior to any undocking/docking actions. This type of docking requires a re-boot in order for the portable computer to recognize peripherals in the docking station. In addition, upgrading the docking station with new peripheral cards means that the user must possess enough technical savvy to understand interrupts and direct memory access (DMA) and be able to physically set configuration jumpers.
The new Plug-and-Play (PnP) standards have made docking and undocking somewhat easier. In systems incorporating "warm docking" capabilities, the portable computer must be placed in a "suspend" or "standby" state prior to docking/undocking. Entry into a standby state is normally accomplished by pushing a button or hot-key on the portable. In a typical standby state, the state of the system is stored in system memory, all devices are placed in a low power state if possible, with power being removed from the floppy drive, the hard drive and most ports. Bus clocks are also disabled, although a lower frequency clock remains active to maintain system memory. By utilizing Plug-and-Play features, the portable computer is able to recognize and activate peripherals when it exits the standby state and without the need to re-boot. The time spent in the standby state, however, is often longer than desirable.
In many docking systems, the portable computer is configured to automatically exit standby mode after a predetermined amount of time. This amount of time must be sufficient for completion of the motorized docking/undocking action, as well as an additional safety margin. Additional time is therefore added to the docking/undocking process because of the requirement to go into standby mode. Currently, no efficient method exists for docking/undocking without first suspending or completely powering off the portable computer system.